Question

以下查询在MySQL中成功执行但在MSSQL中抛出错误。任何人都可以在MSSQL 2008中为我提供等效查询的示例吗？

SELECT DISTINCT TOP 20 
  [users].[id], [users].[email], [users].[first_name], [users].[last_name], 
  (SELECT groups_groups.name 
   FROM users AS groups_users 
     LEFT JOIN users_groups AS groups_users_groups ON groups_users_groups.user_id = groups_users.id 
     LEFT JOIN groups AS groups_groups ON groups_groups.id = groups_users_groups.group_id 
   WHERE users.id = groups_users_groups.user_id) AS [groups] 
FROM [users] GROUP BY [users].[id], [users].[email], [users].[first_name], [users].[last_name] 
ORDER BY [users].[id] DESC

错误：

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression

Answer 1

SQL Server返回该错误，因为您的子查询返回多个值，并且无法在单个记录中为用户分配多个值。

我认为你可以做到以下几点：

检查子查询的逻辑，以便每个用户只返回一条记录。
修复数据，以便子查询只返回一条记录。

Answer 2

也许你的问题可能是子查询返回了多个结果..试试

SELECT DISTINCT TOP 20 
  [users].[id], [users].[email], [users].[first_name], [users].[last_name], 
  (SELECT TOP 1 groups_groups.name 
   FROM users AS groups_users 
     LEFT JOIN users_groups AS groups_users_groups ON groups_users_groups.user_id = groups_users.id 
     LEFT JOIN groups AS groups_groups ON groups_groups.id = groups_users_groups.group_id 
   WHERE users.id = groups_users_groups.user_id) AS [groups] 
FROM [users] GROUP BY [users].[id], [users].[email], [users].[first_name], [users].[last_name] 
ORDER BY [users].[id] DESC

Answer 3

顺便说一句，在MySQL中，该子查询可以简化为......

SELECT DISTINCT g.name FROM groups_groups g

Answer 4

   SELECT users.id as id ,groups_groups.name  into #groups
   FROM users AS groups_users 
   LEFT JOIN users_groups AS groups_users_groups 
       ON groups_users_groups.user_id = groups_users.id 
   LEFT JOIN groups AS groups_groups 
        ON groups_groups.id = groups_users_groups.group_id 
   WHERE users.id = groups_users_groups.user_id

  SELECT DISTINCT TOP 20 
  [users].[id], [users].[email], [users].[first_name], [users].[last_name], g.name
  FROM [users] 
  inner join #groups g  on users.id=g.id 
  ORDER BY [users].[id] DESC

这不是一个经过测试的代码片段，但是从查询中提到的查询看起来像是，如果目标是获取该组用户数据的所有组（复制用户数据但是新的组名）并且将错误抛出为单个字段的子查询返回多个值....如果上面的情况是这样的话基于连接所需的表将所有user.id和groups.name放入临时表，然后执行内部联接以将所有用户数据与基于id的组名组合，以获取所需的数据

MSSQL中的等效SQL查询

4 个答案: